Apparatus for reproducing images



Feb. 12, 196.3 R, M. scHAFFERT 3,077,150

APPARATUS FOR REPRODUCING IMAGES l Filed July 25, 1960 l 41 /Nl/ENTOR Q 3 ROLAND M. SCHAFFERT \4m/ @y M 31 I A77 /VEV United. @arent 3,677,159 APPARATUS FR BEPRDUCENG lll/AGES Roland Schadeit, Saratoga, Calif., assigner to international Business Machines Corporation, New York, NSY., a corporation of New York Filed .uly 25', 1960, Ser. No. 45,653 2 Claims. (Cl. 951.7)

This invention relates to an apparatus for reproducing images on a viewing surface and, more particularly, to such an apparatus including a cathode ray tube for translating images from a master copy to a display or printing surface.

it is a principal object of the invention to provide improved image reproduction apparatus.

' Another object of my invention is to provide a highspeed electronic printer for obtaining low cost, highvolume printing operation.

Still another object of the invention is to provide an apparatus wherein the reproduced or printed image may have any desired size relationship with respect to the master copy image.

1t is yet another' object of the invention to provide reproduction apparatus including a cathode ray tube having an interchangeable character r image plate.

1n one preferred embodiment, the invention provides an apparatus for reproducing images on a print-receiving surface from a master copy comprising a cathode ray tube including a photoconductive plate. The cathode ray tube includes electrode elements for providing an electron beam and directing the beam to scan the photoconductive plate. A coil is mounted on the tube for developing a potential field in the vicinity of the photoconductive plate to form an electron mirror in conjunction with the plate to reflect the electron beams. An electron lens directs the reected electron beam to impinge on a photosensitive screen.

A master copy having images or characters formed thereon is illuminated by a source of light. Light rays reliected from the master copy impinge on the photoconductive plate and develop electrostatic patterns yon the photoconductive plate corresponding to the images on the master.

The electron beam reflected by the electron mirror provides a pictorial representation on the cathode ray screen Vof the image on the master copy. A film of any suitable type may be arranged in a position adjacent the cathode ray tube screen and be exposed thereto to provide a ermanent record of the images formed on the screen.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments of the invention, as illustrated in the accompanying drawings.

In the drawings in which like reference characters refer to like elements throughout:

FIG. l shows an apparatus in accordance with the invention for reproducing images; l FIG. 2 'shows the photoconductive plate 19 of FIG. l in enlarged scale;

` PEG. 3 shows a modification of a structure of FIG. l

in which the light rays are directed through a character slide to form electrostatic patterns on the photoconductive plate;

FiG. 4 shows yet another modification of the structure according to the invention in which a character or image plate has magnetic characters which are to be imaged by 'the electron beam onto the screen of the cathode ray tube.

Referring to FIGV l, which illustrates one embodiment of the invention in schematic form, there is shown a cathode ray tube 11 comprising a V-shaped evacuated envelope 13 having the various electrode elements mounted therein. A cathode 15 for vproviding the electron beam 17 is mounted at the free end of one arrn, the "left-hand arm as oriented'in FIG. l, of the V-shaped envelope 13. The beam controlling electrode 14, the beam accelerating anode '16, the focusing lens 18 and beam deliecting plate system 24, as well as cathodel 15, are conventional and; per se, form no part of the invention. Defiecting plate system 24 comprises four plates mounted to form essentially the sides of a box for `controlling the beam passing therebetween. The beam, indicated by vthedotted lines 17, is projected onto a photoconductive plate 19 mounted at the bight of the V-shapedtube. Ph'otoconductive plate 19 is connected to ground reference through a variable battery 30 which provides a bias to maintain Yplate 19,` which is in effect a semiconductor, at ground potential by cancelling the effect of the electron beam which tends to make plate 19 negative with respect to ground.

Photoconductive plate 19 is shown in an enlarged scale in FIG. 2, and preferably comprises a glass base 19a, a transparent conductive layer 19b, such as tin voxide (S1102), or very thin evaporated metal,'such as aluminum or silver coated on base 19a, and a photoconductive layer 19C coated on'the'trans'pare'nt layer 19b. Layer 19c'may be of any suitable photoconductive materials such as cadmium selenide, cadmium sulde, zinc sulfide or selenium. The battery 30 is connected to the transparent conductive layer 1917. f

A light image projected upward, as oriented in the drawings, onto plate 19`passes through the glass base 19a and through transparent conductor 1,9b to photoconductive layer 19C. Plate 19 thus becomes selectively conductive in conformance with the image pattern formed on the inner surface, thatis, the surface within the tube 11 of the photoconductive layer 19o.

` `A coil 22 circumposed about the right-hand arm of the V-shaped envelope 13 provides a potential field which forms an electron mirror 20 in conjunction with photoconductive plate 19. Mirror 20 stops the beam 17 at the surface of plate 19 and redirects the direction of travel of the beam, as shown by thetdottedlines, toward a photosensitive screen 21 mounted at the free end of the righthand arm of'envelope 13. Electron lens 23, which may be similar to lens 1S and which is of any suitable known type such as the univoltage 'or unipotential lens, focuses the beam 17 onto screen 21. Deflecting plates 26, which are similar to deflecting plates 24 and which are mounted in the right-hand arm of tube 11, control the position at which the beam impinges on screen 21. Screen 21 translates the' impingement of the electron beam thereupon into a light image which can be viewed directly or a permanent record can be made thereof. A low sensitivity, rapid processing film 27 of any suitable known type is arranged to be moved adjacent the screen 21 to be exposed by direct contact with the screen.

' As is known, in acathode ray tube having an electrode configuration for forming and controlling an electron beam, if the potential drops to zero or below zero at any point on the path of the beam, electrons proceeding toward the region of low potential are reversed in their direction and return to the area of higher potential. If

Athe potential eld is arranged such that the electrons are in various directions or demagnetized, magnetic fields will, Vin general, exist about the surface of the tilm. `In such a case, the motion of an electron in the mirror region will be effected by these magnetic fields as well as by the electric field, since a magnetic field exerts a force on an electron moving in the field. The electron mirror will detect the motion of an electron due to such iields and, therefore, the mirror can then serve as a device for reading magnetically stored information.

lf the surface of an electron mirror is an insulator and the electrons are allowed to impinge on the surface with a velocity such thatV the surfaces secondary emission ratio is less than unity, discrete stored charges on the surface may be seen. The discrete areas may either be positive or negative with respect to the surface and they will cause equipotential perturbations equivalent to those which arise from surface irregularities. Thus, the electron mirror can display contact potentials, or surface conductivities and thus, in fact, any condition that will create an irregularity in the equipotential in the mirror surface.

The` invention utilizes the foregoing phenomena to selectively display alphanumeric characters, or other forms of information on the face or screen of a cathode raytube.

Referring to FIG. 1, current from any suitable known source, not shown, is coupled to flow through accelerating coil 22 to cause coil 22 to develop a potential field which is about kv. positive with respect to plate 19,v

which plate is essentially at, that is, close to -ground potential. hus, the beam projected from cathode toward photoconductive plate 19 along the left-hand arm, as oriented in the drawings of the V-shaped tube 11, is stopped at the surface of photoconductive plate 19; the direction of motion of the beam is changed; and the beam is then accelerated upward along the right-hand arm of the V-shaped tube by the field to cause the electron beam to impinge on the screen 21. The electrons will therefore carry an image of the pattern of electrostatic charges that exist on the surface of the plate.

A master copy 29 having characters formed thereon which are to be displayed on screen 21 and/ or printed on the film 27 is mounted in a position adjacent the photoconductive plate 19. The master 29 may be a single page or unit, or it may be any continuous sheet of copy of material that may be moved across a given point. Sources of light 31 of any suitable type illuminate the master 29. The light reflected from the master 29 at a given instance is focused by optical lens 33 to impinge on the photoconductive plate 19. As noted above, the light focused by the lens 33 onto the photoconductive plate 19 will cause electrostatic charges or patterns to be formed on the photoconductive surface of the photoconductive plate 19, which electrostatic charges correspond to the characters on the master 29. The charges formed on the photoconductive plate will vary as the master is moved and correspondingly provide different patterns on the photoconductive plate in response to the characters reflecting the light through the optical lens 33 to the photoconductive plate.

ln PIG. l, the electron beam 17 is caused to scan the photoconductive plate. As is known, the scanning operation of the electron beam 17 may be relatively fast with respect to physical movement of the master 29. Thus, the electron beam reflected from the photoconductive plate 19 will provide a pictorial representation of the electrostatic image formed on photoconductive plate 19. lt will further be appreciated that the image formed on photoconductive plate 19 may have any desired size relationship with respect to master 29; this provides a means of reducing copy to microfilm or microcard size.

While FIG. 1 illustrates electrostatic deflection of the electron beam 17 by deflecting plate systems 2d and 26, it will be recognized that magnetic deflection of the beam, using current carrying coils or yokes, could also be used.

FlG. 3 shows a modification of the structure of FIG. 1 in which a transparent character slide 41 having characiers formed thereon is utilized as the master copy. The tribe structure utilized in FlG. 2 is identical to FIG. l, so only the lower portion of envelope 13 and plate 19 are shown to describe this modification. In FIG. 3, the source of light is positioned to shine through the slide 41 and the light rays emerging from the top of the slide 41 are focused by optical lens 33 to impinge on photoconductive plate 19. lt is possible to change characters rapidly by simply inserting different character slides in position.

The first set of deflection plates 2d control the position at which the electron beam impinges on the photoconductive plate and, by applying the proper voltages to deflection plates 2d, any character or symbol on the character slide 41 can be selected. The electron beam may be arranged to be wide enough to cover an entire individual character area on the photoconductive plate 19, or a small diameter beam may be used arranged to sweep or scan the area of each individual character as it moves or scans over the plate 19.

The deiection plates 26 position the selected characters at the desired spot on the face or screen 21 of the cathode ray tube. By controlling the voltages applied to deflection plates 26, the selected characters can be positioned in any predetermined sequence or array on the screen 21. With the simultaneous application of controlI voltages to the two systems of deflection plates 2d and 26, words, sentences and numbers can be displayed on the screen 21.

FIG. 4 shows another modification of the structure of FIG. l, in which modification a magnetic plate 44 with magnetized characters formed thereon is utilized to provide a master to modify the electron beam. The tube structure employed in FIG. 4 is similar to FlG. l, so only the lower portion of envelope is shown to describe this modification. In this structure, the electron beam on its return path carries an image of the magnetic characters formed on magnetic plate 44 to the screen 21 of the cathode ray tube. Magnetic plate #i4 is connected directly to ground since any charge developed by an electron beam impinging thereon is rapidly dissipated by the rapidly conducting properties of magnetic plate L14. The characters formed on magnetic plate le may be erased and new characters written or formed magnetically on the plate without removing the magnetic plate t4 from the cathode ray tube.

Further, the plate on which the electron beam impinges may have raised characters, intaglio characters, conductive characters or polarized characters formed thereon. From the aforementioned description, it will be appreciated that the electron beam will carry a pictorial representation of the characters thus formed to the screen of the cathode ray tube.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. An apparatus for reproducing images on a printreceiving surface from a master copy comprising, in combination, a cathode ray tube including electron beamforming means, beam-controlling means, electron beamaccelerating means, and a photosensitive screen; a photoconducting plate, said electron beam-controlling means controlling said beam to scan said photoconducting plate; means for developing a potential field in the vicinity of said photoconductive plate to form an electron mirror in conjuntcion with said photoconductive plate, said electron mirror providing a field for stopping said beam in the vicinity of said plate and then causing said beam to be accelerated away from said plate, whereby said beam carries an image of any irregularities existing on said4 plate, said photosensitive screen arranged for receiving said electron beam and translating the impingement of the electron beams into light images; and means for illuminating the master copy and for directing light rays reflected from the master copy to impinge on said photoconductive plate, said light rays developing electrostatic patterns on said photoconductive plate corresponding to the images on said master copy, said electron beam accelerated away from said electron mirror providing a pictorial representation on said screen of the characters on said master copy for exposing the print-receiving surface thereto.

2. An apparatus for reproducing images on a print receiving surface from a master copy comprising, in combination, a generally V-shaped cathode ray tube, said tube including a photoconductive plate mounted in the lbight of said V-shaped tube; means mounted in one arm of said V-shaped tube for providing and controlling an electron beam to be projected along said one arm to scan said photoconductive plate; coil means mounted on the other arm of said tube for developing a potential eld in the vicinity of said photoconductive plate to form, in conjunction with said photoconductive plate, an electron mirror, said electron mirror providing a field for stopping said beam in the vicinity of said plate and then causing said beam to accelerate away from said plate and along said other arm, said beam carrying an image of the sur face irregularities on said plate; a photosensitive screen formed in the free end of said other arm and arranged for receiving said electron beam, said screen translating the impingement of the electron beam into light images; and means for illuminating the master copy and for directing light rays reected from the master to impinge on said photoconductive plate, said light rays `developing electrical patterns on said photoconductive plate corresponding to the images on said master, whereby said electron beam accelerated away from said electron mirror provides a pictorial representation on said screen of the characters on said master to which the print-receiving surface is exposed.

References Cited in the le of this patent UNITED STATES PATENTS 2,699,512 Sheldon J'an. 11, 1955 2,717,971 Sheldon Sept. 13, 1955 2,808,768 Squassoni Oct. 8, 1957 2.901,627 Wiskott Aug. 25, 1959 

1. AN APPARATUS FOR REPRODUCING IMAGES ON A PRINTRECEIVING SURFACE FROM A MASTER COPY COMPRISING, IN COMBINATION, A CATHODE RAY TUBE INCLUDING ELECTRON BEAMFORMING MEANS, BEAM-CONTROLLING MEANS, ELECTRON BEAMACCELERATING MEANS, AND A PHOTOSENSITIVE SCREEN; A PHOTOCONDUCTING PLATE, SAID ELECTRON BEAM-CONTROLLING MEANS CONTROLLING SAID BEAM TO SCAN SAID PHOTOCONDUCTING PLATE; MEANS FOR DEVELOPING A POTENTIAL FIELD IN THE VICINITY OF SAID PHOTOCONDUCTIVE PLATE TO FORM AN ELECTRON MIRROR IN CONJUNCTION WITH SAID PHOTOCONDUCTIVE PLATE, SAID ELECTRON MIRROR PROVIDING A FIELD FOR STOPPING SAID BEAM IN THE VICINITY OF SAID PLATE AND THEN CAUSING SAID BEAM TO BE ACCELERATED AWAY FROM SAID PLATE, WHEREBY SAID BEAM CARRIES AN IMAGE OF ANY IRREGULARITIES EXISTING ON SAID PLATE, SAID PHOTOSENSITIVE SCREEN ARRANGED FOR RECEIVING SAID ELECTRON BEAM AND TRANSLATING THE IMPINGEMENT OF THE ELECTRON BEAMS INTO LIGHT IMAGES; AND MEANS FOR ILLUMINATING THE MASTER COPY AND FOR DIRECTING LIGHT RAYS REFLECTED FROM THE MASTER COPY TO IMPINGE ON SAID PHOTOCONDUCTIVE PLATE, SAID LIGHT RAYS DEVELOPING ELECTROSTATIC PATTERNS ON SAID PHOTOCONDUCTIVE PLATE CORRESPONDING TO THE IMAGES ON SAID MASTER COPY, SAID ELECTRON BEAM ACCELERATED AWAY FROM SAID ELECTRON MIRROR PROVIDING A PICTORIAL REPRESENTATION ON SAID SCREEN OF THE CHARACTERS ON SAID MASTER COPY FOR EXPOSING THE PRINT-RECEIVING SURFACE THERETO. 